With the progress of transistor process technology, the dimension of transistors has shrunk and therefore the number of transistors per unit area of an integrated circuit has increased accordingly. However, the off-state current has dramatically increased with further reduction in the channel length of a transistor, i.e., short channel effect. This effect is the major challenge of further increasing the density of transistors. Reducing the thickness of channel is known as one way of suppressing short channel effect. Two-dimensional (2D) semiconductors are expected to serve as ultra-thin semiconductor channel materials to suppress the short channel effect.